Secondary electron discharge tube



Patented Mar. 28, 1939 2,151,783 SECONDARY ELECTRON DISCHARGE TUBE Edmund Heinrich Liipp, Berlin, Germany, and Adrianus Johannes Wilhelmus Marie van Overbeek, Eindhoven,

Netherlands, assignors to N. V. Philips Gloeilampenfabrieken, Eindhoven,

Netherlands Application June 22, 1937, Serial No. 149,582 In the Netherlands June 22, 1936 2 Claims.

The invention relates to electron discharge tubes which comprise a cathode, one or more control elements, an anode and a so-called secondary emission electrode which is an electrode a beam which is influenced and modulated by the electrode 2 and accelerated by the electrode 3. Secondary electrons emitted by the secondary emission electrode 4, due to bombardment by 5 whose surface may readily emit secondary electhe pimary modulated beams, may flow to the an- 5 trons, and more particularly to the form of ode 5 along the lines indicated by dotted arrows. construction of such a discharge tube, Variations in the primary stream cause in the According to the invention, the anode is not flow of secondary electrons to the anode 5 correlocated in the path of the primary electrons, sponding and magnified variations, which are so that the latter cannot reach it. When all substantially independent of variations in volt- 10 of the secondary electrons are drawn away by age on the anode. the anode, a variation of the anode voltage brings We claim: about only a slight current variation, so that a 1. An electron discharge tube comprising an high internal resistance is obtained. indirectly heated cathode, a control element It is advantageous to utilize a form of con comprising a pair of metal sheets mounted on struction wherein the control and screen element opp sides of said cathode to form a p s a e are in the form of plates or solid elements which for the discharge from said cathode, an accelsurround part of a preferably indirectly heated crating electrode comprising a pair of metal cathode and act as a kind of electron gun, while sheets on opposite sides of and parallel to said the secondary emission electrode is mounted opontrol m n a con y l r mission 20 posite other parts of the cathode in position to electrode in alignment. with the passage between be struck by the beams from the electron gun. the sheets of said control element, and an anode The anode may be arranged outside the path between said secondary electron emission elecof the primary electrons in such manner that trode and the end of said accelerating electrode it can be struck only by the electrons emanating and outside the electron path extending from. 25 from the secondary emission electrode. the cathode through the passage in the control The invention will be understood more easily element to said secondary emission electrode. by reference to the accompanying drawing which 2. An electron discharge tu Comprising a represents diagrammatically in cross section one rectilinear cathode, beam forming means adjaform of construction with the electrodes of a cent said cathode consisting of an equipotential 3o discharge tube arranged according to the inaccelerating electrode comprising a pair of convention. ductors mounted on opposite sides of and parallel Referring to the drawing, l denotes a tubular to said cathode to form the electron discharge indirectly heated cathode inside of which is an from said cathode into an electron beam, said insulated heating element; 2 and 3 denote a conductors being wider than the diameter of 35 control element and a screen or accelerating elecsaid cathode and spaced to provide for said electrode respectively, each of the duplex type with tron beam an unobstructed passage between two solid parts, such as metal sheets, mounted said conductors of a width as great as the spacon opposite sides of the cathode to form a kind ing between said conductors, a unipotential conof electron gun which produces a modulated trol electrode adjacent said cathode and between 40 beam of primary electrons. Opposite the intersaid accelerating electrode and said cathode, a mediate sides of the cathode, which are between secondary electron emitter mounted beyond the the two sheets or parts of the control element 2, ends of said accelerating electrode conductors is located the electrode 4, with the surface exand opposite the passage between said conducposed to the modulated beams coated with a tors and extending across and perpendicular to- 45 secondary electron emission material which the path of said electron beam, and an output readily emits secondary electrons. Outside the anode mounted between said emitter and said P Of t p ry discharge or electron beam, conductors out of alignment with said passage which is lengthwise of and between the two and outside the path of said electron beam to sheets of the control element, and beyond the said emitter. 50

end of the accelerating electrode 3, is an anode 5. As indicated in the drawing by broken line arrows, the primary electrons may flow from the cathode to the secondary emission electrode 4 in EDMUND HEINRICH LoPP.

ADRIANUS J OHANNES WILHELMUS MARIE VAN OVERBEEK. 

